Weapon proficiency

Weapon proficiency is a passive attribute in Borderlandsthat a character can build for each weapon type. Characters gain proficiency for the equipped weapon whenever experience is gained from a kill. This applies even if the kill is scored by an allied unit, including a team mate, a Bloodwing or a Scorpio Turret. Kills scored from standard melee attacks and grenades also count towards the class of the weapon currently wielded.

Bonuses

The formulas, and the process used to determine them, have not been confirmed.

Each proficiency level gives you three bonuses for every weapon in that category, which affect different weapon characteristics:

Damage - Adds to the weapon's 'Manufactured Damage'.Reload Speed - Decreases the time it takes to swap out a weapon's magazines.Accuracy - Improves the character's handling of the weapon. See Accuracy.Stability - Exclusive to Sniper Rifles, Stability decreases the time it takes for a rifle to 'settle' after lining up the scope, after firing a shot and after taking damage.[1][2]Cooldown Rate - Exclusive to Eridian Weapons, Cooldown reduces the time it takes an Eridian weapon to recharge.Rate of Fire - Increases the rate at which a weapon can fire one shot after another. While not exclusive to any one weapon type, Shotguns and Sniper Rifles earn a rate-of-fire bonus for proficiency.

Notes

Weapon proficiencies are not affected by kills in Mad Moxxi's Underdome Riot, due to the lack of experience gained from kills in that area.

Brick does not gain weapon proficiency experience while using Berserk as he has no weapon equipped while in his berserk state.

There is a bug for PC users where simply mousing over the sniper proficiency bar will not show the bonuses of the weapon proficiency. Instead, left clicking the sniper proficiency displays its bonuses, as does using the up/down arrow keys to select the sniper bar.

Prior to release, higher proficiencies were meant to lower the level requirements to equip guns of that category. Although this feature was removed and has no effect on the game, when a weapon is equipped, the "Level Requirement" field on the weapon's item card is shown lower than it really is. Players can un-equip the weapon to check the actual required level.

Characters do not receive proficiency if a teammate kills an enemy while players are in a menu.